Bio 112 Primates (Humans)

Evolutionary Relationship of Primates

  • Definition of Primates:
    • Diverse group with approximately 300 species, including lemurs, monkeys, apes, and humans.
    • Habitat: Varied, found in terrestrial and tropical regions. Humans occupy terrestrial habitats.
    • Key Characteristics:
    • Evolved as arboreal insectivores (tree-living insect eaters).
    • Two defining features:
      • Grasping fingers and toes (in contrast to clawed feet).
      • Binocular vision for depth perception (eyes positioned at the front of the face).

Groups of Primates

  • Major Extant Groups:

    • Lemurs & lorises
    • Tarsiers
    • Anthropoids (monkeys, apes, humans)

  • Anthropoids:

    • Defining traits:
    • Diurnal (most primates are nocturnal).
    • Color vision.
    • Larger brains relative to body size.
    • Feed on fruits and leaves, forming complex social structures with long-term parental care.
    • Divergent Groups:
    • New World Monkeys: Migrate from Africa to South America around 30 MYA.
    • Old World Monkeys: Ground-dwelling and arboreal, possess no prehensile tails, and have downward-pointing noses.

Hominoids vs. Monkeys

  • Hominoids: Include apes and hominids.
    • Traits of Apes:
    • Larger brains than monkeys.
    • Lack of tails.
    • Size is generally larger than monkeys, except for gibbons.
    • Evolutionary Path:
    • Apes evolved from Old World monkeys approximately 22 MYA and again migrated back to Africa 10 MYA, leading to modern African apes (gorillas, chimpanzees).

Comparison: Apes vs. Hominids

  • Hominid Characteristics:
    • Bipedal locomotion vs. knuckle-walking in apes and palm walking in monkeys.
    • Anatomical differences include:
    • More curved vertebral column.
    • Spinal cord positioning (exits at the base of the skull).
    • Broader pelvis for stability and weight distribution.
    • Proportions: 35% lower limb body weight in hominids versus 18% in apes.

Evolutionary History of Homo Species

  • Genus Australopithecus:

    • Oldest known hominids, existing 6-7 MYA primarily in Africa.
    • Characteristics: Small body (~18 kg, ~1 m tall), similar brain size to apes.

  • Genus Homo:

    • Evolved from Australopithecus approximately 2 MYA.
    • Key species:
    • Homo habilis: 2.2 - 2.6 MYA, known as "handy man" with tools.
    • Homo erectus / Homo ergaster: 1.8 MYA - 250,000 YA, more advanced culturally with social structures and tools.
    • Homo neanderthalensis: Evolved 500,000 YA, lived alongside Homo sapiens with tools and burial practices indicative of culture.
    • Homo sapiens: First evidence ~100,000 YA, fully anatomically modern with advanced social organization and art.

Migration Patterns of Hominids

  • Homo sapiens began migrating out of Africa approximately 60,000 years ago, reaching various continents:

    • Europe: Arrived 45,000 - 35,000 years ago.
    • Asia: Migration patterns reflect adaptability to environments.
    • North America: Crossed to this region approximately 13,000 years ago.

  • Key Features of Homo sapiens:

    • Coexistence with Homo neanderthalensis, sharing 4% of their genomes.
    • Progressive dispersal to all corners of the Earth, molded by environmental factors and technological innovations in navigation and survival.

Fossil Evidence

  • Earliest Evidence of Homo sapiens: Found in Israel, dating back to approximately 90,000 - 100,000 years ago.
  • Distinct Features of Homo sapiens:
    • Modern body size, facial features, and brain capacity (~1,350 cm³).
    • Evidence of cultural practices like burial rituals and creation of art, marking symbolic thinking.

Summary of Major Species within Genus Homo

  • Homo habilis: 2.2 MYA, small build, tool user.
  • Homo erectus: 1.8 MYA - 250,000 YA, advanced tools and social structures, migration.
  • Homo neanderthalensis: Evolved 500,000 YA, possibly shared cultural traits with H. sapiens.
  • Homo sapiens: Modern humans, coexisting with Neanderthals, showing advancements in society and technology.